Vacuum Leak?, Still breathing, Why??? |
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Vacuum Leak?, Still breathing, Why??? |
kkid |
Jan 6 2009, 12:47 AM
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#1
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Member Group: Members Posts: 343 Joined: 18-December 07 From: Oakland, CA Member No.: 8,483 Region Association: Northern California |
I've been skeptical if there is some vacuum leak since the warm idle still goes up and down about ±50~100.
So I covered the air inlet on the air cleaner housing completely but the engine was still running as if nothing happened. Does this mean there is a huge air leak or is it designed to breath the air from somewhere else???? Thanks in advance (IMG:style_emoticons/default/pray.gif) |
Dave_Darling |
Jan 6 2009, 01:47 AM
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#2
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
Huge air leak from somewhere. All the air getting into the engine "should" be coming from the air filter housing. If you blocked that off, then it's coming from somewhere else...
--DD |
kkid |
Jan 6 2009, 02:05 AM
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#3
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Member Group: Members Posts: 343 Joined: 18-December 07 From: Oakland, CA Member No.: 8,483 Region Association: Northern California |
Thanks DD!
But I don't see any other holes other than air cleaner inlet. That must be huge. I've recently changed inner injector seals, intake runner gasket & hoses and other vacuum hoses. What could be the problems? (IMG:style_emoticons/default/confused24.gif) |
SLITS |
Jan 6 2009, 07:44 AM
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#4
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
1.) Expansion hoses on the plenum to runners
2.) Crack in the plenum 3.) Runner to head spacer/gasket 4.) Throttle body gasket 5.) Any number of defective hoses that connect directly to the plenum |
kkid |
Jan 6 2009, 07:35 PM
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#5
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Member Group: Members Posts: 343 Joined: 18-December 07 From: Oakland, CA Member No.: 8,483 Region Association: Northern California |
Hello Ron, Thanks for the advise. I'll follow your guidance but...some questions came up.
1.) Expansion hoses on the plenum to runners >Mines are new but I did not put clamps on them. I can feel by touching the air outlets on the plenum and intake runners are not perfectly aligned so the hoses may be stressed and leaked. Better to use the the clamps? 2.) Crack in the plenum >What's the easiest way to inspect the dusty plenum? Just carb spray on them? 3.) Runner to head spacer/gasket >I installed new one while ago but I did not use gasket sealer or anything on either side. Is this causing the air leak? 4.) Throttle body gasket >It looked tired so I cut a gasket paper and replaced today but no change. 5.) Any number of defective hoses that connect directly to the plenum >They are all new but I will triple check and get back here. Thanks (IMG:style_emoticons/default/pray.gif) |
ericread |
Jan 6 2009, 07:40 PM
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#6
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The Viper Blue 914 Group: Members Posts: 2,177 Joined: 7-December 07 From: Irvine, CA (The OC) Member No.: 8,432 Region Association: Southern California |
How about removing the air cleaner and closing off the air intake with your hand. If the engine dies, great. That means you are looking in the right place (cleaner/hoses). If not, you've got a serious plenum leak or throttle body leak.
Eric |
kkid |
Jan 7 2009, 01:22 AM
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#7
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Member Group: Members Posts: 343 Joined: 18-December 07 From: Oakland, CA Member No.: 8,483 Region Association: Northern California |
Yeah, you're right, Eric.
The engine died in a split second as I blocked the TB. So I looked around the engine bay and found 3 suspicious points. 1) The rubber sleeve that goes into the bottom of the air cleaner outlet is not complete in the slit. There is about 1/8" room to go but it's so tight and does wanna go in. 2) I recently replaced the air filter(Mahle) and checked today. The rounded rubber edge of the top of filter does not look like being pressed at once. It is too clean. And there is no gasket between the air cleaner housing halves. Is this normal??? 3)One hose comes from canister in the front may be disconnected and vacuum cleaning in the rocker panel. The rocker's never been opened in its life. Which one do you think the most suspect? Any input would be appreciated. Thanks! (IMG:style_emoticons/default/pray.gif) |
SLITS |
Jan 7 2009, 08:03 AM
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#8
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
All of the items you mentioned are pre-TB / plenum and would not have an effect on the idle.
You never stated if the idle oscillates or just sometimes it's a little higher than others. If it is a steady oscillation at idle (hunts @ idle), I would suspect: 1.) Point cam bushing in distributor is worn allowing side to side slop and the timing/dwell is changing (pretty obscure) 2.) To low of fuel pressure (lean mixture) or to high of fuel pressure (rich mixture) 3.) Injectors not flowing a same rate 4.) Trigger points could could be fouled If it is when you come off the throttle while driving (ie, coming to a stop sign or light) ... a transient condition 1.) Throttle cable is sticking slightly 2.) Gunk around butterfly shaft in TB is not allowing it to return to same positiion each time. Hey, just guessing at things I would check ........... +/- 50 to 100 rpm is not a major problem ... irritating, but not a great problem. These things are not electronically controlled sophisicated engine management systems and they are old. Anyway, read the article in the link that follows: PBanders D-Jet Site And bookmark it. |
ericread |
Jan 7 2009, 11:27 PM
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#9
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The Viper Blue 914 Group: Members Posts: 2,177 Joined: 7-December 07 From: Irvine, CA (The OC) Member No.: 8,432 Region Association: Southern California |
(IMG:style_emoticons/default/agree.gif)
It doesn't seem to be a TB/Plenum issue. Work the issues above and let us know what you find... Eric |
kkid |
Jan 12 2009, 01:49 AM
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#10
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Member Group: Members Posts: 343 Joined: 18-December 07 From: Oakland, CA Member No.: 8,483 Region Association: Northern California |
Huge air leak from somewhere. All the air getting into the engine "should" be coming from the air filter housing. If you blocked that off, then it's coming from somewhere else... --DD Does your motor stop running if the air inlet on the air cleaner housing is blocked off? I'm assuming you have a same model with D-jet set up like mine. So you are being asked as my role model. Thanks (IMG:style_emoticons/default/pray.gif) |
Spoke |
Jan 12 2009, 08:02 AM
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#11
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Jerry Group: Members Posts: 6,991 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
Find vacuum leaks fast with carb cleaner. Spray on hoses, connections and listen for a change in engine note.
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kkid |
May 15 2009, 12:07 AM
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#12
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Member Group: Members Posts: 343 Joined: 18-December 07 From: Oakland, CA Member No.: 8,483 Region Association: Northern California |
I have been ignoring this issue since the car runs just fine. But the injector flow rate result from the injector cleaning service shows that one injector sprays more than other 3. So that is the reason for this hunting.
And today, I accidentally located 2 hair cracks on the top of the plenum where the 2 holes are seen. So I plugged JB weld in it. I will be happy to open the idle speed screw since it is closed almost to the limit. Thanks for the all advises! |
ConeDodger |
May 15 2009, 09:09 AM
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#13
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Apex killer! Group: Members Posts: 23,612 Joined: 31-December 04 From: Tahoe Area Member No.: 3,380 Region Association: Northern California |
Did you look at the bottom of the plenum? These things rust out and can have pin holes in them that can barely be seen.
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EdwardBlume |
May 15 2009, 10:18 AM
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#14
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914 Wizard Group: Members Posts: 12,338 Joined: 2-January 03 From: SLO Member No.: 81 Region Association: Central California |
Plenums get tweeked when you don't have the accelerator stop on the floorboard, and an aggressive foot overtorques the throttle repeatedly. Ask me how I know. (IMG:style_emoticons/default/driving.gif)
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